1. Field of the Invention
The present invention relates to a load control device for controlling the amount of power delivered to an electrical load, and more particularly, to a dimmer switch having a visual display, such as a single visual indicator or a linear array of visual indicators, for providing a visual indication of energy savings or usage information.
2. Description of the Related Art
A conventional wall-mounted load control device is mounted to a standard electrical wall box and is coupled between a source of alternating-current (AC) power (typically 50 or 60 Hz line voltage AC mains) and an electrical load, such as, a lighting load. Standard load control devices (such as dimmer switches) use one or more semiconductor switches, typically bidirectional semiconductor switches, such as triacs or field effect transistors (FETs), to control the current (and ultimately the power) delivered to the load, and thus, the intensity of the light provided by the lighting load between a maximum intensity and a minimum intensity. The semiconductor switch is typically coupled in series between the source and the lighting load. Using a phase-control dimming technique, the dimmer switch renders the semiconductor switch conductive for a portion of each line half-cycle to provide power to the lighting load, and renders the semiconductor switch non-conductive for the other portion of the line half-cycle to prevent current from flowing to the load. The ratio of the on-time, during which the semiconductor switch is conductive, to the off-time, during which the semiconductor switch is non-conductive, determines the intensity of the light produced by the lighting load.
Wall-mounted dimmer switches typically include a user interface having a means for adjusting the lighting intensity of the load, such as a linear slider, a rotary knob, or a rocker switch. Dimmer switches also typically include a button or switch that allows for toggling of the load from off (i.e., no power is conducted to the load) to on (i.e., power is conducted to the load), and vice versa.
When controlled to an intensity below the maximum intensity, the dimmer switch is operable to save energy since less power is being delivered to the lighting load. In fact, if a connected lighting load is controlled to approximately 85% of the maximum possible intensity of the lighting load, the dimmer switch provides an energy savings of approximately 15% of the maximum possible power consumption of the lighting load. In addition, the difference between the maximum possible intensity and 85% of the maximum possible intensity is barely perceptible to the human eye. However, many users of dimmer switches unintentionally control the intensity of the lighting load to a level that is higher than actually needed, i.e., to a level that provides more light than is needed, thus, wasting energy. Therefore, there is a need for a dimmer switch that provides a visual indication of energy savings or usage information, such that the user is able to make a knowledgeable, intentional decision of the desired lighting intensity to energy.